Apparatus for modifying vapor super-heat temperatures



Sept. 25,1956 P. H. KOCH 2,764,137

APPARATUS FOR MODIFYING VAPOR SUPERHEAT TEMPERATURES Filed Feb. 19, 1952 2 Sheets-Sheet 1 FIG.1

INVFNTOR Paul fijfociz BY ATTORNEY United States Patent APPARATUS FOR MODIFYING VAPOR SUPER- HEAT TEMPERATURES Paul H. Koch, Bernardsville, N. J., asslgnor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application February 19, 1952, Serial No. 272,400 6 Claims. (Cl. 122-478) The present invention relates to fluid heat exchange apparatus, and more particularly to the construction and arrangement of a convection vapor superheater associated with a vapor generator.

Convection vapor superheaters are customarily installed with sufficient heat absorbing surface to give an optimum delivered vapor temperature based on burning some definite type of fuel. However, it is frequently found that changes in the fuel or other factors so change the heating gas temperatures and quantities delivered to the heat absorbing surfaces that the resulting vapor temperature may be excessive or deficient.

In accordance with the invention, the convection superheater is positioned transversely of a major portion of a heating gas pass lea ding from a furnace to the convection vapor generating tube bank. Along the margin of the superheater, adjacent the side walls of the gas pass, unrestricted gas flow areas are provided, the extent of the gas flow area being adjustable as required to effect the division of gas flow therethrough and over the superheating surface. Adjustment of the gas flow area is accomplished by removal or addition of sections of a baffle which are cooperatively maintained in operative position by the tube section; of the adjacent superheater element and vapor generating tubes which line the outer wall of the gas pass.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described an embodiment of my invention.

Of the drawings:

Fig. 1 is a side elevation, in section, of a vapor generating and superheating unit incorporating the present invention;

Fig. 2 is a section plan view taken on the line 2-2 of Fig. 1; i

Fig. 3 is a section elevation taken on the line 3-3 of Pig. 2;

Fig. 4 is a section elevation taken on the line 44 of Fig. 3; and

Fig. 5 is an enlarged view taken on the line 5-5 of Fig. 4.

In the embodiment of the invention illustrated in the drawings, the pendent convection superheater is installed in the gas fiow path between a furnace 11 and banks of vapor generating tubes 12, in a boiler of known type. The furnace shown is constructed for the combustion of solid fuel which is delivered thereto by a spreader Stoker indicated generally at 13.

As shown in Figs. 1 and 2, each wall of the furnace 11 is lined by a row of vapor generating tubes connected into the circulatory system of the boiler. The rows of tubes 14 and 15 lining opposite side walls are upright and extend between lower and upperheaders, such as the ice headers 16 and 17 of the tube row 14, (see Fig. 1). The lower headers are connected with the lower drum 20 of the boiler by downcomers 21 while the upper header is connected with the upper drum 22 by a conduit 23. Downcomer tubes 24 from the drum 20 open to a header 25 which in turn is connected with a header 26 by tubes 27.

"The rear wall tubes 28 open to the header 25, are upwardly disposed in the lower portion of the furnace and are inclined inwardly of the furnace 11 at a position intermediate their height to form a forwardly extending arch structure 30. Some of the tubes 28 extend upwardly from the end portion of the bridge wall 30 to form two rows 255A of widely spaced tubes to provide a slag screen across the gas outlet 32 of the furnace 11 and thereafter extend rearwardly to open into the drum 22. Other tubes 28B of the rear wall tubes 28 are inclined rearwardly to line the upper surface 33 of the arch structure 30, and thereafter extend upwardly across the heating gas flow path to open into the drum 22.

The superheater It? is installed between the rows of tubes 28A and 28B in the heating gas pass formed between the upper surface 33 of the arch structure 30 and an extension of the roof 29 of the furnace, which is lined by the upper portions of the tubes 34 of the front wall 35 of the furnace 11. As shown in the drawings, the elements of the superheater are formed of fiat coils of tubes lying in parallel upright planes which are generally parallel to the flow of heating gases passing from the furnace outlet 32 toward the convection tube banks 12 of the boiler. The fiat coil elements have multiple loops providing heating surfaces sufiicient to heat the steam to the desired temperature, and each coil element receives saturated steam from a steam inlet header 36 and discharges to an outlet header 37. The headers are horizontally disposed above the roof 29 of the gas pass, with the inlet header 36 receiving saturated steam from the drum 22 through a row of tubes 38.

The tubular coil elements of the superheater 10 are uniformly spaced transversely of the heating gas pass with the outermost elements thereof spaced from the side walls of the gas pass. The spaces 40 on each side of the superheater extend the full vertical extent of the gas pass, have a width approximating three or four times the spacing between superheater elements, and are bounded by the outermost elements of the superheater and the side walls lined by the rows of tubes 14 and 15. As shown in Figs. 2 and 3, the outermost elements are formed of two tube circuits arranged in a common plane, such as tubes 59 and 51, with upright lengths 50A and 50B of the tube 50 spaced apart so that the intertube space therebetween is substantially equal to and in horizontal alignment with the intertube space of the opposite side wall tubes 14A and 148.

A vertically aligned tier 41 of superposed refractory closure members 42 and 44 is supported on the upper face of arch 33, extends transversely across each of the spaces 40 and between tube sections 50A and 50B and tube sections 14A and 1413. The width of the closure members is suflicient to result in a slight flexure of tube sections 50A and 50B so that the members are held therebetween. One end of the closure member abuts the tube sections of the adjacent superheater elements, and the opposite ends bear on the refractory wall section outside of the row of tubes 14. By this arrangement the sev eral superposed closure members are adequately supported against displacement due to changes in temperature of related parts or due to any gas pressure differential occurring under operating conditions.

The tiers 41 extend for a portion only of the vertical height of the gas pass, and openings with closures 47, as indicated in Figs. 1 and 3, are provided in the sidewalls "invention.

rperature.

forconvenient access'to'the spaces 40 so that the height of-the--tiers may bemodified as required to adjust the distribution of the heating gas flow through the gas pass; The superheater heat absorption and the final superheat temperaturc for-a given gas flow from the furnace it may thus-bemodifie'd as desired by changes in the height of the'-'tiers-41; an increase in height thereof causing a greater "proportion of gas to-flow over the superheater, and vice versa.

'In the arrangement shown the lowermost closure member 42, which is not subject to front and embrasureby the tube elements 50A and 50B, is supported and positioned ontubes 288 in the upper face of arch 33 by moldable refractory material '43, which is air setting and heat' resistant, to maintain closure member 42 in proper position.

'Inthe bodyof the superheatenas shown in Figs. 1 and 2,"theeletnents arefo'rme'd in part from single tube circuits and in part from double tube circuits. At their end connections tothe headers 36 and 37, the tubes 52! and *53,- for example, he in a plane normal to the longitudinal axis'of the headers. The tubeportions adjacent the saturated steam'header 36 are displaced transversely of the gas ,pass to form closely spaced superheater elements, while in'the coil loop approaching the header 3'7 the tubes "52 and53 are bent into a common plane with the element spacing substantially doubled.

Spacer bars 45 (see Fig. 1) are positioned on the tubes 52'and 53 near the upper end portion of the coil loops to maintain thealignment and spacing of the superheater elements, and a tie bar 46 connects the tubes 233 with the adjacent leg of the superheater elements. Similar spacer bars 48.011'the tubes 50 and 51, and tie bars 49 connecting tubes 28Band 50 are shown in Fig. 3. With this construction the element spacing and the spacing between'legs .of each superheater tube coil is maintained generally uniform in the closely spaced portion of the superheater bank .10, .even though operation of the unit will tend to .cause differential expansion between the steam igenerating tubes, such as 28B, and the superheater tube coil elements.

The steam flow paths through tubes and 51 from L inlet header 36 to outlet header 37, as compared with the fflowpaths through the elements formed of tubes 52, will :have:a greater mass flow, contributing to adequate cooling of the tubes 50 and 51 which are subjected to greater heat transmission inthelengths adjacent the relatively unrestricted gas fiowpassages' along the sidewalls. With relatively low superheat temperatures, it is not necessary to re duce the lengthof the tubes SO-and 51 compared with -the length of tubes 52 and 53 to avoid overheating tube metal, as shown in the illustrated embodiment of the However, in the majority of installations, it isdesirable to utilize the construction shown.

-In the operation of a unit of the type described, the amount of'superheater surface is selected to obtain the desired steam superheat temperature, and the tiers 41 are constructedto have a height of approximately one half the height of the heating gas pass. After operation of the unit-has been stabilized, members 44 of tier 41 may be "added or removed to obtain the desired superheat tem- Adding orremoving members 44 is considerably simpler than .adding to or subtracting from the amount of heating surface in the superheatiug elements, and if a change of fuel necessitates further adjustment of thetier 41 height, this is easy to accomplish.

While in accordance with the provisions of the statutes "I have illustrated and described herein the best form of *the invention'now known tome, those skilled in the art willunders'tand that changes may be made in the form of the apparatus disclosed without departing from the spirit I claim:

1. In a vapor generator, the combination of vapor generating tubes positioned along the inner surface of walls defining the top and bottom and sides of a heating gas pass, a dependent convection superheater including a plurality of parallel rows of flat tubular coil elements disposed in planes generally parallel to the direction of gas flow through .said heating :gas pass and extending substantially from top to bottom of said gas pass, an outermost element of said superbeater being spaced from the adjacent wall or ziiigas pass, and means for adjusting the how of heating gas through said superheater elements comprising removable sectional closure members positioned and supported by vapor generating tubes in the side wall and bottom of said .gas passand said outermost element of said superheatcr.

2. in a vapor generator, the combination of a row of upright vapor generating tubes positioned along the inner surface of walls defining the sides of a heating gas pass, a dependent convection superheater including a plurality of parallelelements of flat tubular coils disposed in planes generally parallel to the direction of gas flow through said heating gas pass and extending substantially from top to bottom of said gas pass, the outermost elements or" said superheater being spaced from the adjacent walls of said gas pass, and means for adjusting the cross-sectional flow area through .said heating gas pass comprising a tier of removable transverse closure members extending upwardly from the bottom of said gas pass, between adjacent vapor generating tubes in a gas pass side wall and between adja- 7 cent parallel superheater tubes in said outermost element.

3. In a vapor generator, the combination of a row of upright vapor generating tubes defining the side and top and bottom walls of a heating gas pass, a dependent convection superheater including a plurality of parallel elements of fiat tubular .coils disposed in planes generally upright and parallel to the direction of gas flow through said heating gas-pass and extending substantially from top to bottom of said gas pass, the outermost elements of said superheater :being spaced from the adjacent side wall of .saidgaspass, andmeans-foradjusting the cross-sectional fiow area through said'gas pass comprising sectional closure members supported upon a row of vapor generating tubes-at .the bottom of said gas pass and extending into said heating .gas pass from a position between adjacent .tubes in said side wall to a position between adjacent parallel lengths of said outermost superheater elements.

4. In a vapor generator, the combination, of vapor generating tubes positioned along the inner surface of walls defining a heating gas pass, a vapor superheater including a plurality. of elements of flat tubular coils disposed in planes generally parallel to the direction of gas flow through said heating'gas pass and extending substantially from top to bottom of said gas pass, an outermost element of said superheater being spaced from the :adjacent wall of said gas pass, each element in the body of said superheater being formed by a continuous tubular coil, said outermost element of said superheater being formed by two continuous tubular coils each having a developed length less than the tubular coil length in the body of said superheater, and means for adjusting the cross-sectional flow area through said gas pass cornfacevof each, a row of tubes in the front of said furnace extending -in a horizontally inclined direction to define the roof of .said.-furnace,,the row of tubes in the rear of said furnace shaped todefine an arch projecting inward- 13 of said furnace with tubes in said row forming an upwardly extending slag screen row projecting across a gas outlet from said furnace between the arch and the furnace roof, other tubes from said rear wall row of tubes extending upwardly from said arch across said furnace gas outlet at a position rearwardly spaced from said slag screen, a superheater positioned in said furnace gas out let between said spaced vapor generating tubes and extending substantially from top to bottom of said furnace gas outlet, the superheater elements adjacent the side walls of said furnace outlet being spaced therefrom, and 2. tier of removable closure members positioned between each of said furnace outlet side walls and the adjacent superheater element and supported upon the upper surface of said arch. 4

6. In a vapor generator including a furnace chamber enclosed by walls including rows of generally upright vapor generating tubes connected in the circulatory system of said vapor generator, the row of tubes in one of said furnace walls shaped to define an arch projecting inwardly of said furnace with tubes from said tube row forming an upwardly extending row of slag screen tubes projecting across a gas outlet from said furnace and p0- sitioned between the arch and the furnace roof, other tubes from said row of furnace wall tubes extending upwardly from said arch in a row across said furnace gas outlet at a position spaced from said row of slag screen tubes in the direction of gas flow from said furnace, a superheater positioned in said furnace gas outlet between said spaced rows of tubes and extending substantially from top to bottom of said furnace gas outlet, said superheater including a plurality of elements consisting of multi-loop tubes disposed in planes generally parallel to the direction of heating gas flow through said furnace outlet, the multi-loop superheater tube element adjacent the side Wall of said furnace outlet being spaced therefrom, removable transverse closure means supported upon the upper arch surface formed by said furnace Wall tubes, and positioned between adjacent vapor generating wall tubes and adjacent portions of said superheater element spaced therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,096,090 Bell May 12, 1914 1,250,181 Jacobus Dec. 18, 1917 1,735,464 Keithley Nov. 12, 1929 2,403,237 Powell et al. July 2, 1946 2,563,489 Rowand Aug. 7, 1951 2,597,203 Taylor May 20, 1952 FOREIGN PATENTS 537,198 Great Britain June 12, 1941 

